linux-kernel - Re: [PATCH v2 09/12] gpio: sim: new testing module

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Date:   Mon, 8 Mar 2021 15:23:31 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Joel Becker <jlbec@...lplan.org>, Christoph Hellwig <hch@....de>,
        Shuah Khan <shuah@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Kent Gibson <warthog618@...il.com>,
        Jonathan Corbet <corbet@....net>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-doc <linux-doc@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH v2 09/12] gpio: sim: new testing module

On Fri, Mar 5, 2021 at 11:15 AM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> On Thu, Mar 04, 2021 at 09:15:29PM +0100, Bartosz Golaszewski wrote:
> > On Thu, Mar 4, 2021 at 2:15 PM Andy Shevchenko
> > <andriy.shevchenko@...ux.intel.com> wrote:
> > > On Thu, Mar 04, 2021 at 11:24:49AM +0100, Bartosz Golaszewski wrote:
> > > > From: Bartosz Golaszewski <bgolaszewski@...libre.com>
>
> > > > +
> > > > +     /*
> > > > +      * FIXME If anyone knows a better way to parse that - please let me
> > > > +      * know.
> > > > +      */
> > >
> > > If comma can be replaced with ' ' (space) then why not to use next_arg() from
> > > cmdline.c? I.o.w. do you have strong opinion why should we use comma here?
> > >
> >
> > My opinion is not very strong but I wanted to make the list of names
> > resemble what we pass to the gpio-line-names property in device tree.
> > Doesn't next_arg() react differently to string of the form: "foo=bar"?
>
> It's ambiguous here.
>
> So, the strings '"foo=bar"' and 'foo=bar' (w/o single quotes!) are indeed
> parsed differently, i.e.
>         '"foo=bar"' -> 'foo=bar',
> while
>         "foo=bar" -> 'foo' + 'bar'.
>

IMO '"foo", "bar", "", "foobar"' looks better than '"foo" "bar" ""
"foobar"' and I'm also not sure next_arg will understand an empty
quote?

If you're not objecting strongly, then I would prefer my version.

> ...
>
> > > > +     ida_free(&gpio_sim_ida, id);
> > >
> > > Isn't it atomic per se? I mean that IDA won't give the same ID until you free
> > > it. I.o.w. why is it under the mutex?
> > >
> >
> > You're right but if we rapidly create and destroy chips we'll be left
> > with holes in the numbering (because new devices would be created
> > before the IDA numbers are freed, so the driver would take a larger
> > number that's currently free). It doesn't hurt but it would look worse
> > IMO. Do you have a strong opinion on this?
>
> It's not strong per se, but I would rather follow the 2nd rule of locking:
> don't protect something which doesn't need it.
>

OK, makes sense.

> --
> With Best Regards,
> Andy Shevchenko
>
>